Ceramic coated muffler and method of making it



Oct. 22, 1963 R. L.PLACEK 3,107,743

CERAMIQCOATED MUFFLER AND METHOD OF MAKING IT Filed Jan. 3, 1961 INVENTORS RAYMOND L. PLAcsK, jkoms A. DANNEIZ AND James C. ARTHUR w snduefik A-r-roramzvs.

United States Patent 3,107,748 CERAMIC COATED MUFFLER AND METHOD OF MAKING IT Raymond L. Placek, Thomas A. Dunner, and James C.

Arthur, Columbus, Ind., assignors to Arvin Industries,

Inc, Columbus, Ind., a corporation of Indiana Filed Jan. 3, 1961, Ser. No. 89,299

5 Claims. (Cl. 181-61) This invention relates to a ceramic coated mufiler construction and to a method of making it.

As is well known in the muiile-r industry, it is desirable to treat or coat mufflers with a protective material to increase their resistance to corrosion and thus give them an extended life. One of the more common ways of extending the life of a muffler isthe application of a coating of procelain or other ceramic material to the internal and external surfaces of the mufiler, such as is disclosed in Kuhn Patent No. 2,395,006 and Bryant Patent No. 2,825,- 421.

The methods heretofore employed in the mufiier industry for applying such ceramic coatings to rnufilers, however, have had certain deficiencies. Certain of the methods require individually coating the individual components or a mufller prior to their assembly which thus necessitates numerous handling and transfer operations making such process relatively expensive. Other methods employed require the mufiler to be either partially or completely assembled and for certain of the assembled components to have relatively small topenin gs formed therein so that the coating material can flow through the muffler to reach the surfaces thereof. Because of the size of the openings involved, this coating operation requires a relatively long time cycle in order for the coating material to flow through the muffler, and even then the coating material fails to reach some of the mufiler interstices.

It is thus a general object of our invention to provide a muffler construction and a method of coating it which will overcome the difficulties and disadvantages discussed above. More specifically, it is an object of our invention to provide a ceramic coated muffler which will have auniform coating over its entire surf-ace, and which will have the desired acoustical properties. It is a further object of our invention to provide a method of applying a ceramic coating to a mufiler which can be quickly and easily carried out on a production line basis, which will ensure they 2 formation of a uniform coating of ceramic material over said muffler, and which will provide such coating without adversely affecting the acoustical properties of the muffier.

Our invention is adapted to apply a ceramic coating to a mufller of the general type comprising an elongated? "1 connecting said chambers.

According to our invention'we coat such a 'mufiier by firstforming a plurality of relatively large openings in the muffler battle and end plates in positions such that supporting a plurality of gas conduitsoperatively inter-r;

said openings will be disposed in alignment with each other s. 1

when the muffler is assembled. The assembled muffier is subjected to a series of cleaning operations, after which it may be coated with a thin film of nickel. ll'he muffle-r is then dipped in a slurry of a ceramic material which flows through and around it to dispose a thin coating of the t ceramic material IOTJ. all of theinternal and external muffler surfaces. The mufiler is then subjected to drying and baking operations to bake on the ceramic coating. After the ceramic coating has been baked, a tube is inserted V throughthe plurality of aligned openings in the baffle ice 2 and end plates and is rigidly fixed in place. The tube closes the openings to thus prevent said openings from adversely affecting the sound attenuating properties of the acoustic chambers donned by the b-aflle plates.

Other objects and features of our invention will become apparent from the more detailed description which follows and from the accompanying drawing, in which:

FIG. 1 is a longitudinal section of a muffler embodying our invention;

FIG. 2 is an end elevation of the muffler shown in FIG. 1; i

FIG. 3 is a longitudinal section of the muffler shown in FIG. 1, but withits axially extending tube removed therefirom; and

FIG. 4 is an enlarged fragmentary vertical section showing the interconnection between the axially extending tube and one of the end plates.

As shown in the drawing, our ceramiccoated mufiler comprises an elongated outer shell 10 having its ends enclosed by end plates 12.. A plurality of baffle plates 14 are rigidly secured to the inner faces of the shell 10 and define a plurality of acoustic chambers 16 for attenuating the noise level of the exhaust gases passing through the muffler. The end plates 12 support inlet and outlet gas conduits 18 and 20, and the baffle plates :14 support gas conduits 22 which dispose the several chambers .16 in operative comunication with each other.

Our novel muffler construction differs from conventional mufiier constructions in that prior to assembly We form a plurality of openings 25 in the end andb afile plates,

said openings being relatively large having diameters of about one inch. The openings 25 are oriented on the end and baffle plates so that when the mufiler is assembled said openings are disposed in alignment with each other throughout the length of the mufiler. Conveniently, as shown in FIG. 2, the openings 25 are formed and de lined by axially extending nipples 27 formed in end and baffle plates 12 and 14. A second series of openings 26 are fmdiscriminately formed in the baflle plates 14 and are substantially smaller than the openings 25, having diameters ranging up to a maximum of about one-eighth inch.

The muffler construction just described is assembled as shown in FIG. 3 and is the-n subjected to a sequence of conventional preparatory and ceramic coating operations. Such a sequence first begins with cleaning the mother by soaking it in a boiling alkaline solution for several minutes, after which it is subjected to one or more water rinses to remove any residual alkali therefrom. A second cleaning step follows in which the: muffler is soaked for several minutes in an acid bath maintained in an elevated temperature, after which the mufller is again subjected to one or more water rinses. After the acid treatment, the mufiler is soaked in a neutralizing solution, such as forexample an aqueous solution of soda ash and borax maintained at an'elevated temperature,

to ensure against the possibility of any acid or alkali remaining in the muffler.

flashed, as by soaking it in a bath of an aqueous solunon-01" nickel sulphate maintained at an elevated temperature. This createsa thin depository nickel coating onthe mufiler to provide a better surface for adherence of theceramic coating onto the muffler.

After the nickel coating has been applied, the mufller is thoroughly dried and is then ready for the application of a ceramic coating to its surfaces. The ceramic coating is applied by dipping the mufiler into a slurry of the desired ceramic material. Desirably, such slurry may comprise a suspension of finely ground frit in water hava 3 ing' a consistency of heavy paint. The slurry flows through and around the muffler to thus coat all of its surfaces, and the excess slurry is then allowed to drain from the mufiier leaving a thin coating of the ceramic material disposed over all of the internal and external surfaces of the muflier. With the muffler thus coated, hot dried air is forced through and over it to remove the excess moisture from the deposited coating, and the coated mufiler is then baked in an oven maintained at about 1500 F. to fuse the ceramic coating. These operational steps of cleaning, nickel flashing, and coating are all conventional well known practices employed in the coating industry, and thus the precise materials and method techniques employed in any one or all of these steps may be adjusted as desired.

During all of these processing steps, the liquid materials employed rapidly fiow through the relatively large openings 25 in the muffler so that said liquid material can reach all of the interstices of'the mufiler. The openings 26 form vent openings to prevent the formation of air blocks which would impede the flow of liquid through the mufiier. Theopenings 25 and 26 not" only provide means forensuring that the liquids reach all of the interstices of the mutller, but in addition, the'openings V provide a napid fluid-flow passage through the mufiler,

.said mufiler in order that the suspended ceramic particles do not'settle out of'the suspension and 'thereby create anonuniform coating. The openings 25,,however, being relatively large, permit the slurry to be quickly drained from themuffler before the suspended ceramic particles can settle out, thus ensuring a uniform thickness of the ceramic coating on the mufller.

After the muffler has been coated in the manner just described, the openings 25 are closed by an elongated tube 28, which has been previously .ceramic coated. As shown in FIG. 2, the tube 28 has an outer diameter corresponding'to the diameters of the openings 25 and nipples 27 so that when said tube is inserted in the mufiler it completely closes all of the openings 25 in the bafile plates 14 and end plates 12, with said nipples 27 providing spaced axially extending supports for said tube. With both the nipples 27 and tube 28 being coated, the

'joints formed at their interconnections will thus be provided with a protective coating reducing their susceptibility to corrosion; Conveniently, in order to fixedly mount the tube 28 in the muffler, the outwardly projecting end plate nipples 27 support the ends of the tube 28, and said tube ends are provided with a plurality of circumferentially spaced tongues 32 'crimpe-d over said nipples.

Thus,;:the openings 25 remain open during the coating sequence to'provide a fluid-fiowpassage for the liquids moving through the muffler to ensure that all 'of the interior surfaces of said mufiler are reached by said liquids; to ensure a rapid movement of said liquids through the mufiler; and to ensure a uniform ceramic coating ceramic is used generically and includes'porcelain enamels, glass, frit, and the like.

We claim as our invention:

1. .A ceramic coated muffler, comprising a unitary elongated continuous outer shell, a pair of end plates closing the opposed ends of said shell and supporting exhaust inlet andoutlet conduits, a plurality of bafile plates mounted within the shell and dividing the shell interior into a plurality of acoustic chambcrs, a plurality of elongated conduits mounted on said bathe plates and operatively interconnecting said plurality of acoustic chambers, means extending the length of said muliler through a plurality of aligned openings formed in said bafile and .end plates and closing the same, and a ceramic coating on the surfaces of said mufiler and its components.

2. A ceramic coated mufiler, comprising a unitary elongated continuous outer shell, a pair of-end plates closing the opposed end-s of said shell and supporting exhaust inlet and outlet conduits, a plurality of baffle plates mounted within the shell and dividing the shell'iuterior into aplura-lity of acousticchambersa plurality of elongated conduits mounted on said baffle plates and operatively interconnecting said plurality of acoustic chambers, an elongated tube extending the length of the mufiler through a plurality of aligned openings formed in said 'bafile and end plates and closing the same, the openings in said end plates being defined by nipples projecting out of the general planes of said end plates with the ends of said tube being rigidly mounted therein, and a ceramic coating on the surfaces of said mufller and its compo- I nents.

3. A ceramic coated mufiler, comprising a unitary elongated continuous outer shelhapair of end plates closing theopposed ends of said shell and supporting exhaust inlet and outlet conduits, a plurality of baffle plates mounted within the shell and dividing the shell interior into a plurality of acoustic chambers, a plurality of elongated conduits mounted on said bafileplates and operaporting exhaust inlet and outlet conduits and housing a plurality of acoustic chambers interconnected by a plurality of conduits and separated from each other by baffie plates, comprising the steps of forming a plurality of openings in said lbaffie and end plates whereby upon muffler assembly said openingswill be disposed in alignment,,assembling said mufiler, removing the contaminants I from the surfaces of said mufiler, dipping said mufller in a slurry of ceramic material andcoatingthe interior and exterior exposed mufiler surfaces with said slurry," heat on all of the interior surfaces of the muflier. However,

after said coating sequence, the openings 25 are closed by'the tube 28 so that said, openings do not interfere with or decrease the silencing of the exhaust gases by the acoustic chambers 16, and in addition, prevent excessive'gas leakage through'the end plates. Some or all ofthe small diameter vent openings 26 may be closed by coating material, but because of their small diameters, these openings :26-which are not closed will not adversely alfect the operation or efficiency of the acoustic have described our treating said mufiler to dry said slurry and bake the ceramic. material therein, said openings providing continuous fluid-flow passages through said mufller during said contaminant-removing, dipping, and heat-treating 5.- A method of makinga ceramic exhaust inlet and outlet conduits and housing a plurality of acoustic chambers interconnected by a;plurality of conduits and separated from each other by baflle plates,

comprising the steps of forming a first set of small di-' ameter openings in said bafile plates and a second set of relatively large diameter openings in said end and baffle plates whereby upon mufiler assemblysaid second set of openings will be disposed in alignment, assembling said,

mother, removing the contaminants from the surfaces of said mufiler, dipping said mufller in a slurry of ceramic material and coating the interior and exterior exposed mufiler surfaces with said slurry, heat treating said muffler to dry said slurry and bake the ceramic material thereon, said second set of openings providing continuous fluidfiow passages through said muifler during said contaminant-removing, dipping and heat-treating steps and said first set of openings providing vent openings for said fluid-flow, and inserting a ceramic coated tube through said second set of openings to close the same, said tube being rigidly connected to said end plates.

References (Ji ted in the file of this patent UNITED STATES PATENTS FOREIGN PATENTS Australia Feb. 10, 1948 

1. A CERAMIC COATED MUFFLER, COMPRISING A UNITARY ELONGATED CONTINUOUS OUTER SHELL, A PAIR OF END PLATES CLOSING THE OPPOSED ENDS OF SAID SHELL AND SUPPORTING EXHAUST INLET AND OUTLET CONDUITS, A PLURALITY OF BAFFLE PLATES MOUNTED WITHIN THE SHELL AND DIVIDING THE SHELL INTERIOR 